Adjustable booster seat



FIG. 1 is a top plan view of a booster seat showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a side elevational view, the opposite side being a mirror image thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a bottom view thereof. 

The ornamental design for an adjustable booster seat, as shown and described. 